Multiple gas detection device

A multiple gas detection device comprises: a first cell part provided with a first electrochemical cell; a second cell part provided with a second electrochemical cell; a third cell part provided with a third electrochemical cell; an inlet diffusion controller controlling diffusion of measured gas; and a measured gas chamber into which the measured gas flows through the inlet diffusion controller. The first cell part is configured to selectively detect a concentration of NOx or ammonia contained in measured gas in the measured gas chamber. The second cell part is configured to discharge oxygen contained in measured gas in the measured gas chamber and convert NO2 and ammonia contained in measured gas in the measured gas chamber to NO. The third cell part is configured to detect a concentration of NO contained in measured gas in the measured gas chamber.